This invention relates to the field of power generation, and more specifically to a system for choosing between two or more electrical generators when starting a parallel generator power system.
Electrical generators or generator sets are devices which transform mechanical energy into electrical energy. A typical generator set includes an engine, driven by a fuel such as gasoline, and a rotating shaft driven by the engine. The rotating shaft develops electric power, which is then used to power an electrical load.
Sometimes, two or more generator sets are connected to a common bus in a parallel arrangement. This allows for each of the generator sets to be turned on as needed. For instance, if a light load is being fed, then only one generator set may be needed. As the load increases, a second generator set, a third generator set, and so on can be activated.
In such parallel generator set systems, a signal is sometimes received by the system to start more than one of the generator sets at a time. However, when two or more generator sets are started simultaneously, it becomes necessary for the system to determine which generator set has started first and allow that generator set to close its circuit breaker to the bus while inhibiting the other generator sets in the system from closing their breakers. This is because the generator sets cannot be simultaneously connected to the bus since their output must be synchronized in voltage, frequency, or phase before being connected to the load. Accordingly, a single generator set must be connected to the load at a time. In the past, a central control module was connected to each generator set to control the generator set connections to the bus. However, such a central controller does not allow a parallel system to be easily expanded and it can be costly to set up and maintain.
What is needed is a system and method for connecting multiple generators to a common load in which there is no central controller so that it is easier to set up a parallel generator power system and easier to add further generators onto the system without having to re-configure the whole system.
Accordingly, the present invention provides a method and system for connecting multiple generator sets to a shared bus. One aspect of the present system involves a power system. In one embodiment, a power system includes two generator sets and two modules, wherein each of the two modules is associated with one of the two generator sets. Each of the two modules is configured to receive a signal from that module""s associated generator set when that module""s associated generator set is ready to energize the bus. Each of the two modules also includes an output to send a signal which allows that module""s associated generator set to connect to the bus. The modules are connected together and configured so that when each of the modules receives the signal that the module""s associated generator set is ready to energize the bus at substantially the same time, each of the two modules performs a method which provides that only one of the two modules is permitted to send the signal which allows that module""s associated generator set to energize the bus.
Another aspect of the present system provides a method for connecting one of a plurality of generators to a bus. In one embodiment, a method includes providing a plurality of substantially equivalent connection modules, each of the plurality of connection modules associated with one of the plurality of generator sets, each of the plurality of connection modules configured to send a signal to its associated generator set when the connection module reaches a first-start state. The method further includes connecting each of the plurality of connection modules to its one or two neighboring connection modules to allow the connection modules to communicate with each other.
Among other advantages, the present system allows the power system to be quickly set up and easily expanded by providing separate connection control modules on each generator set instead of having a central controller.